Polyamide-based transparent composition

ABSTRACT

The invention relates to a transparent composition comprising, by weight, the total being 100%:  
     5 to 40% of an amorphous polyamide (B) which results essentially from the condensation of at least one optionally cycloaliphatic diamine, of at least one aromatic diacid and optionally of at least one monomer chosen from:  
     α,ω-aminocarboxylic acids,  
     aliphatic diacids,  
     aliphatic diamines,  
     0 to 40% of a supple polyamide (C) chosen from copolymers containing polyamide blocks and polyether blocks and copolyamides,  
     0 to 20% of a compatibilizer (D) for (A) and (B),  
     (C)+(D) is between 2% and 50%,  
     with the condition that (B)+(C)+(D) is not less than 30%,  
     the difference to 100% being a semi-crystalline polyamide (A).  
     The invention also relates to the articles obtained, such as plates, films, sheets, tubes and profiles, to the articles obtained by injection-moulding and in particlular to the films and sheets which are then bonded onto skis.  
     The invention also relates to the above articles decorated, for example, by sublimation, and coated with a transparent protective layer consisting of the composition of the invention.

FIELD OF THE INVENTION

[0001] The present invention relates to a polyamide-based transparentcomposition. The present invention also relates to the articles obtainedfrom this composition and to processes for preparing such articles.Polyamides are polymers that are widely used for their numerousproperties. Specifically, polyamides have some or all of the propertieslisted below: transparency, impact strength, tensile strength and/orcompressive strength, high resistance to external attack, such as bycold, heat, chemical agents, UV radiation in particular, and the like.Thus, polyamide-based articles such as, for example, spectacle frames,various types of casing, motor vehicle equipment, surgical equipment,packaging, sporting and ski articles, in particular a ski topsheet, haveappeared. These articles should usually carry various inscriptions, forinstance the characteristics of the product sold in the case of apackaging made of polyamide. These products should also often bedecorated.

[0002] One example of a product which needs to be decorated is a ski, inparticular the topsheet. It has thus naturally been sought to decoratethe polyamides according to the techniques usually used and inparticular that of sublimation. This technique, known as decoration bysublimation or heat transfer, consists in coating the article to bedecorated with a layer of pigments at a temperature of between 80° C.and 220° C., and in heating the assembly to a given temperature. Thepigments are said to be sublimable, but this technique is effective withpigments which can migrate into the structure of the polymer. In pointof fact, a person skilled in the art understands this term “decorationby sublimation” without it being necessary to go into further detailhere. The temperature to which the article to be decorated is broughtshould be high enough to bring about the sublimation or heat transfer ofthe pigments, which may then penetrate, by diffusion, into the structureof the polymer, if this polymer is of suitable morphology. Needless tosay, the polymer should withstand the temperature used during thedecoration by sublimation.

THE PRIOR ART AND THE TECHNICAL PROBLEM

[0003] The polyamides of the prior art do not always have the requiredproperties to be decorated by sublimation. If the polyamide iscrystalline or semi-crystalline, it withstands high temperatures and theoften harsh conditions for carrying out decoration by sublimation may beused with this polyamide. However, crystalline or semi-crystallinepolyamides are not transparent and their opacity makes them unsuitablefor use when transparency is desired. If the polyamide is amorphous, itis thus transparent and, on account of this transparency, may besuitable in applications in which this transparency property is desired.However, when the temperature used for the sublimation is below theglass transition temperature, the polyamide does not have a sufficientlydisorganized structure and the sublimable pigments diffuse into thepolyamide bulk with difficulty. The resulting colour is pale and thusunsuitable for marketing. When the temperature used for the sublimationis higher than the glass transition temperature, the polyamide becomesunacceptably deformed and is thus unsuitable for the use for which it isnormally intended.

[0004] Patents FR-A-2 575 756 and FR-A-2 606 416 disclose amorphouspolyamide compositions based on BACM (bis(4-aminocyclohexyl)methane),BAMCM (bis(3-methyl-4-aminocyclohexyl)methane) or other cycloaliphaticdiamines, isophthalic or terephthalic acid, and other polyamides. Thesepolyamides have transparency properties and are useful for manufacturingmoulded articles. The said document describes a moulding temperaturewhich may be as high as 310° C.

[0005] Patents JP-60-215 053 and 60-215 054 disclose and claim alloyscomprising, on the one hand, a transparent polyamide and, on the otherhand, a crystalline polyamide. The transparent polyamide consists ofaliphatic units as essential monomer component, which are chosen fromlauryllactam, 12-aminododecanoic acid and 11-aminoundecanoic acid, andcyclic units. The examples given for these transparent polyamidesinclude, as cyclic units, a cycloaliphatic diamine,bis(4-aminocyclohexyl)methane and an aromatic diacid, isophthalic acid.The crystalline polyamide consists of Nylon-12 and/or Nylon-11, or ofcopolyamide having a 12 and/or 11 unit as essential monomer.

[0006] Patent FR-A-2 021 910 discloses polyamide compositions comprisingfrom 40% to 99% by weight of an amorphous polyamide based on aromaticacids and 2,2,4- and/or 2,4,4,-trimethylhexamethylenediamine and 60% to1% by weight of an aliphatic polyamide. The articles obtained aretransparent, show good rigidity and are impact- and water-resistant. Thepolyamides are used for the manufacture, by moulding, of hollow articlessuch as bottles. The temperatures used are conventional temperatures.

[0007] U.S. Pat. No. 4,404,317 discloses polyamide compositions such as6,I/6,T/BACM, I/BACM, T which have properties that are useful formanufacturing articles. These polyamides are obtained by blending at atemperature of between 270° C. and 300° C. According to the saiddocument, the blends have properties of resistance to solvents, heatstability and conservation of the mechanical properties under wetconditions. U.S. Pat. No. 4,404,317 discloses blending conditions, suchas the temperature, for various polyamides; in particular, it isrecommended not to exceed 300° C. on account of the degradation of thecrystalline polyamide and also of the amorphous polyamide. It is alsoknown that crystalline polyamides (including PA-12 or PA-6,12) have adegradation temperature of about 270° C., both for injection-mouldingand for extrusion. This temperature may be raised for very brief periodsor in the presence of a stabilizer to a temperature of about 300° C.

[0008] Patent EP 0 628 602 discloses blends of amorphous polyamide andof semi-crystalline polyamide. The examples were carried out on a Werner30 twin-screw extruder equipped with a blender section, at a materialtemperature of 330 to 340° C., starting firstly with a semi-crystallinepolyamide PA-11 with an inherent viscosity of 1.38 dl/g and secondlywith an amorphous semi-aromatic polyamide PA-12/BMACM, T/BMACM, I. Thelatter polyamide is synthesized by melt-polycondensation starting withbis(3-methyl-4-aminocyclohexyl)methane (BMACM), lauryllactam (L12) andisophthalic and terephthalic acid (IA and TA) in a 1/1/0.3/0.7 molarratio. This amorphous polyamide has a glass transition temperature of170° C. and an inherent viscosity of 1.05 dl/g. The blends leaving theWerner extruder die are cooled in the form of rods in a tank filled withcold water, cut into granules and heated at 80° C. under vacuum for 12hours so as to remove the moisture.

[0009] The prior art has disclosed either semi-crystalline polyamides oramorphous polyamides, or alternatively mixtures thereof.Semi-crystalline polyamides and amorphous polyamides are unsuitable forarticles which need to be decorated by sublimation. As regards blends ofsemi-crystalline polyamides and of amorphous polyamide, the amorphouspolyamide always contains aromatic units, generally isophthalic acid orterephthalic acid, which necessitates the use of high temperatures toblend them, resulting in a risk of degradation and a cost which isproportionately higher the higher the temperature.

[0010] A polyamide-based transparent composition has now been foundwhich consists essentially of a blend of semi-crystalline polyamide, ofan amorphous polyamide containing units which are aromatic diacidresidues and of at least one product chosen from supple polyamides andcompatibilizers for the semi-crystalline polyamide and for the amorphouspolyamide. That is to say that, compared with the prior art in which thealiphatic polyamide and the amorphous polyamide can only be blended athigh temperature, it has been found that, if a semi-crystallinepolyamide, an amorphous polyamide containing units which are aromaticdiacid residues and at least one product chosen from supple polyamidesand compatibilizers for the semi-crystalline polyamide and for theamorphous polyamide are blended simultaneously, a transparentcomposition is obtained at a compounding temperature which is lower thanin the prior art, and thus the products do not degrade. Anotheradvantage is that the compositions are more supple while at the sametime remaining transparent.

[0011] The present invention relates to a transparent compositioncomprising, by weight, the total being 100%:

[0012] 5 to 40% of an amorphous polyamide (B) which results essentiallyfrom the condensation of at least one optionally cycloaliphatic diamine,of at least one aromatic diacid and optionally of at least one monomerchosen from:

[0013] α,ω-aminocarboxylic acids,

[0014] aliphatic diacids,

[0015] aliphatic diamines,

[0016] 0 to 40% of a supple polyamide (C) chosen from copolymerscontaining polyamide blocks and polyether blocks and copolyamides,

[0017] 0 to 20% of a compatibilizer (D) for (A) and (B),

[0018] (C)+(D) is between 2% and 50%,

[0019] with the condition that (B)+(C)+(D) is not less than 30%,

[0020] the difference to 100% being a semi-crystalline polyamide (A).

[0021] The term “transparent” corresponds to a coefficient of lighttransmission of greater than or equal to 50%, measured at 560 nm and fora thickness of 2 mm. It is preferably ≧80%.

[0022] The term “polyamide” used in the present description also coverscopolyamides, which may contain third monomers in a proportion whichdoes not affect the essential qualities of the polyamides.

[0023] The term “semi-crystalline” covers (co)polyamides which have botha glass transition temperature Tg and a melting point m.p.

[0024] The term “amorphous” covers polyamides which change to the liquidor molten state, and thus which may be used, above their Tg. Inprinciple, these polymers do not have an m.p. in DSC. However, they mayhave one, but, if they do, its intensity is negligible and does notaffect the essentially amorphous nature of the polymer.

[0025] The definitions according to the present invention are inaccordance with those commonly accepted in the art. Reference will bemade advantageously to the publication “ENPLAs, Booklet on EngineeringPlastics”, section 2.1, pp. 12-13, Ed. 1991 published by “The JapanEngineering Association”. The composition of the invention has manyadvantages:

[0026] It is semi-crystalline like the polyamide (A), i.e. it can bedecorated by sublimation. The crystalline structures are small enoughfor the composition to be transparent.

[0027] It is not too rigid like the semi-aromatic polyamides of theprior art. Its modulus of flexure may be between 1 400 and 600 MPa, themeasurement being made on a sample conditioned for 15 days at 23° C. and50% RH (relative humidity). Specifically, PA 11 has a modulus of flexureof 1 000 MPa, which is considered as average by comparison with a rigidpolyamide with a modulus of flexure of 2 000 MPa and a supple polyamidewith a modulus of flexure of 500 MPa.

[0028] It is ductile, has good impact strength and crack resistance, andalso good abrasion resistance. An article such as a sheet will besuitable for the various shaping operations (cold moulding, swaging)which may be required to obtain a finished product such as a ski.

[0029] Furthermore, it has low moisture sensitivity, essentially since,for (A), the monomers used contain at least 9 carbon atoms, for example:PA11, PA12, PA10.12, coPA10/9.12. By virtue of the semi-crystallinenature of (A), it has good chemical resistance, good cracking stressresistance and good ageing resistance.

[0030] It is easy to manufacture since the temperature at which there isformation of a transparent material is lower than the compoundingtemperature (melt blending in an extruder or a mixer) of thesemi-crystalline polyamide (A) and of the amorphous polyamide (B) in theabsence of (D). The compounding temperature is proportionately lower thelarger the amount of (D) in the composition.

[0031] The advantage of this lower temperature is that there is nodegradation, the composition does not yellow, it has few problems orgels, if any, and the composition is easier to recycle (it may undergo anew use more easily).

[0032] It is very easily used, typically by extrusion. The properties ofthe molten material are adequate (sufficient viscosity) and stable (nofluctuation during the production of the article) and there are no fumesor deposits, unlike certain transparent polyamide compositions of theprior art.

[0033] The invention also relates to articles consisting of thecomposition of the invention, such as plates, films, sheets, tubes andprofiles, to the articles obtained by injection-moulding and inparticular to the films and sheets which are then bonded onto skis.

[0034] The invention also relates to the above articles decorated, forexample, by sublimation, and coated with a transparent protective layerconsisting of the composition of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] As regards the semi-crystalline polyamide (A), mention may bemade (i) of aliphatic polyamides which are the products of condensationof an aliphatic α, ω-amino-carboxylic acid, of a lactam or the productsof condensation of an aliphatic diamine and of an aliphatic diacid and(ii) other polyamides provided that they are semi-crystalline. Amongthese other semi-crystalline polyamides, the ones that are preferred arethose which have crystalline structures that are small enough to beclose to transparency; by way of example, mention may be made of the PAPACM-12 in which PACM denotes para-aminodicyclohexylmethane and 12denotes the C 12 diacid.

[0036] By way of example of aliphatic α, ω-aminocarboxylic acids,mention may be made of aminocaproic acid, 7-aminoheptanoic acid,11-aminoundecanoic acid and 12-aminododecanoic acid. As examples oflactams, mention may be made of caprolactam, oenantholactam andlauryllactam. As examples of aliphatic diamines, mention may be made ofhexamethylenediamine, dodecamethylenediamine andtrimethylhexamethylenediamine. As examples of aliphatic diacids, mentionmay be made of adipic acid, azelaic acid, suberic acid, sebacic acid anddodecanedicarboxylic acid.

[0037] Among the aliphatic polyamides, mention may be made, by way ofexample and in a non-limiting manner, of the following polyamides:polycaprolactam (PA-6); poly-undecanamide (PA11); polylauryllactam(PA-12); poly-butyleneadipamide (PA-4,6); polyhexamethyleneadipamide(PA-6,6); polyhexamethyleneazelamide (PA-6,9);polyhexa-methylenesebacamide (PA-6,10); polyhexamethylene-dodecanamide(PA-6,12); polydecamethylenedodecanamide (PA-10,12);polydecamethylenesebacanamide (PA-10,10) andpolydodecamethylenedodecanamide (PA-12,12).

[0038] Advantageously, (A) is derived from the condensation of a lactamcontaining at least 9 carbon atoms, of an α, ω-aminocarboxylic acidcontaining at least 9 carbon atoms or of a diamine and a diacid suchthat the diamine or the diacid contains at least 9 carbon atoms.Advantageously, (A) is PA 11 or PA 12 and preferably PA 12. It would notconstitute a departure from the context of the invention if (A) was ablend of aliphatic polyamides.

[0039] According to another advantageous form, (A) is an equilibratedpolyamide. The names of the polyamides are recalled below according totheir end groups.

[0040] According to their process of manufacture and/or the chainlimiter used, the polyamides may have excesses of acid or amine endgroups or may even have a proportion of alkyl or other end groups, forexample aryl or any other function, deriving from the structure of thelimiter chosen. The excess of acid end groups derives from a diacidchain limiter. The excess of amine end groups derives from a diaminechain limiter. A primary amine chain limiter leads to a polyamide chainhaving an alkyl end group and an amine end group.

[0041] The name diamine polyamide, PAdiNH₂, refers to a polyamide whichsatisfies the following criteria:

[0042] it has a certain amount of chains ending on both sides with anamine group (NH₂)

[0043] the amount of chains ending on both sides with an amine group(NH₂) is greater than that of the diacid chains (if any)

[0044] the concentration of amine groups is greater overall than theconcentration of acid groups

[0045] a PAdiNH₂ is obtained by adding a diamine as chain limiter or, inthe case of polyamides based on diamine and on diacid such as, forexample, PA6-6, by adding more diamine comonomer than diacid comonomer.

[0046] These polyamides are thus also known for simplicity as PA diamineor PAdiNH₂.

[0047] A polyamide is referred to as a diacid for the opposite reasons.

[0048] A polyamide is equilibrated if

[0049] a limiter or an excess of one of the comonomers has not beenadded

[0050] if the concentration of amine and of acid is essentiallyequivalent.

[0051] To determine the nature of the end groups of a polyamide and thepercentage of chains having these end groups, it is possible to use theknown methods for determining the molar masses, such as, for example,SEC (steric exclusion chromatography) and the methods for assaying amineand acid functions. In the present application, the term SEC denotes themeasurement of the molecular masses of polymers by steric exclusionchromatography, this technique and more particularly its application topolyamides and polyamide block polyethers being disclosed in “Journal ofLiquid Chromatography, 11(16), 3305-3319 (1988)”. As regards thedetermination of the end groups, for example for PA 6, the sample isdissolved in a solution of phenol in methanol and the amines aretitrated with a solution of para-toluenesulphonic acid in methanol. Forthe acid end groups, again for PA 6, the sample is dissolved in benzylalcohol and the acid functions are titrated with a solution of potassiumhydroxide in benzyl alcohol.

[0052] As regards the amorphous polyamide (B), it results essentiallyfrom the condensation of at least one optionally cycloaliphatic diamineand of at least one aromatic diacid. Examples of aliphatic diamines havebeen given above; the cycloaliphatic diamines may be isomers ofbis(4-aminocyclohexyl)methane (BACM),bis(3-methyl-4-aminocyclohexyl)methane (BMACM) and2-2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP). The other diaminescommonly used may be isophorone diamine (IPDA) and2,6-bis(aminomethyl)norbornane (BAMN). Examples of aromatic diacidswhich may be mentioned are terephthalic acid (T) and isophthalic acid(I).

[0053] The amorphous polyamide (B) may optionally contain at least onemonomer chosen from:

[0054] α, ω-aminocarboxylic acids,

[0055] aliphatic diacids,

[0056] aliphatic diamines,

[0057] these products have been described above.

[0058] Examples of (B) which may be mentioned are the amorphoussemi-aromatic polyamide PA-12/BMACM, TA/BMACM, IA synthesized by meltpolycondensation using bis(3-methyl-4-aminocyclohexyl)methane (BMACM),lauryllactam (L12) and isophthalic acid and terephthalic acid (IA andTA). It would not constitute a departure from the context of theinvention if (B) was a mixture of several amorphous polyamides.

[0059] As regards the supple polyamide (C) and first the copolymerscontaining polyamide blocks and polyether blocks, these result from thecopolycondensation of polyamide blocks containing reactive end groupswith polyether blocks containing reactive end groups, such as, interalia:

[0060] 1) Polyamide blocks containing diamine chain ends withpolyoxyalkylene blocks containing dicarboxylic chain ends.

[0061] 2) Polyamide blocks containing dicarboxylic chain ends withpolyoxyalkylene blocks containing diamine chain ends obtained bycyanoethylation and hydrogenation of aliphatic dihydroxylatedalpha-omega polyoxyalkylene blocks known as polyether diols.

[0062] 3) Polyamide blocks containing dicarboxylic chain ends withpolyether diols, the products obtained in this particular case beingpolyetherester-amides. The copolymers (C) are advantageously of thistype.

[0063] The polyamide blocks containing dicarboxylic chain ends arederived, for example, from the condensation of α, ω-aminocarboxylicacids, lactams or dicarboxylic acids and diamines in the presence of achain-limiting dicarboxylic acid.

[0064] The number-average molar mass {overscore (M_(n))} of thepolyamide blocks is between 300 and 15 000 and preferably between 600and 5 000. The mass {overscore (M_(n))} of the polyether sequences isbetween 100 and 6 000 and preferably between 200 and 3 000.

[0065] The polymers containing polyamide blocks and polyether blocks mayalso comprise randomly distributed units. These polymers may be preparedby the simultaneous reaction of the polyether and the polyamide-blockprecursors.

[0066] For example, polyetherdiol, a lactam (or an α, ω-amino acid) anda chain-limiting diacid may be reacted in the presence of a small amountof water. A polymer is obtained essentially containing polyether blocks,polyamide blocks of very variable length, and also the various reagentswhich have reacted randomly and which are distributed randomly along thepolymer chain.

[0067] Whether these polymers containing polyamide blocks and polyetherblocks are derived from the copolycondensation of polyamide andpolyether blocks prepared beforehand or from a one-pot reaction, theyhave, for example, Shore D hardnesses which may be between 20 and 75 andadvantageously between 30 and 70 and an intrinsic viscosity of between0.8 and 2.5 measured in meta-cresol at 250° C. for an initialconcentration of 0.8 g/100 ml. The MFIs may be between 5 and 50 (235° C.for a 1 kg load).

[0068] The polyetherdiol blocks are either used without modification andare copolycondensed with polyamide blocks containing carboxylic endgroups, or they are aminated in order to be converted intopolyetherdiamines and condensed with polyamide blocks containingcarboxylic end groups. They may also be blended with polyamideprecursors and a chain limiter to make polymers containing polyamideblocks and polyether blocks with randomly distributed units.

[0069] Polymers containing polyamide blocks and polyether blocks aredisclosed in patents U.S. Pat. No. 4 331 786, U.S. Pat. No. 4 115 475,U.S. Pat. No. 4 195 015, U.S. Pat. No. 4 839 441, U.S. Pat. No. 4 864014, U.S. Pat. No. 4 230 838 and U.S. Pat. No. 4 332 920.

[0070] Three types of copolymer containing polyamide blocks andpolyether blocks may be distinguished. According to a first type, thepolyamide blocks containing dicarboxylic chain ends are derived, forexample, from the condensation of α, ω-aminocarboxylic acids, of lactamsor of dicarboxylic acids and diamines in the presence of achain-limiting dicarboxylic acid. As an example of anα,ω-aminocarboxylic acid, mention may be made of aminoundecanoic acid,as examples of lactams, mention may be made of caprolactam andlauryllactam, as examples of dicarboxylic acids, mention may be made ofadipic acid, decanedioic acid and dodecanedioic acid, and as an exampleof a diamine, mention may be made of hexamethylenediamine.Advantageously, the polyamide blocks are made of polyamide 12 or ofpolyamide 6.

[0071] According to a second type, the polyamide blocks result from thecondensation of one or more α, ω-aminocarboxylic acids and/or of one ormore lactams containing from 6 to 12 carbon atoms in the presence of adicarboxylic acid containing from 4 to 12 carbon atoms, and are of lowmass, i.e. they have an {overscore (M_(n))} of from 400 to 1 000. Asexamples of α, ω-aminocarboxylic acids, mention may be made ofaminoundecanoic acid and aminododecanoic acid. As examples ofdicarboxylic acids, mention may be made of adipic acid, sebacic acid,isophthalic acid, butanedioic acid, 1,4-cyclohexyldicarboxylic acid,terephthalic acid, the sodium or lithium salt of sulphoisophthalic acid,dimerized fatty acids (these dimerized fatty acids have a dimer contentof at least 98% and are preferably hydrogenated) and dodecanedioic acidHOOC—(CH₂)₁₀—COOH. Examples of lactams which may be mentioned arecaprolactam and lauryllactam. Polyamide blocks obtained by condensationof lauryllactam in the presence of adipic acid or dodecanedioic acid andwith an {overscore (M_(n))} of 750 have a melting point of 127-130° C.

[0072] According to a third type, the polyamide blocks result from thecondensation of at least one α, ω-aminocarboxylic acid (or a lactam), atleast one diamine and at least one dicarboxylic acid. The α,ω-aminocarboxylic acid, the lactam and the dicarboxylic acid may bechosen from those mentioned above. The diamine may be an aliphaticdiamine containing from 6 to 12 atoms and may be arylic and/or saturatedcyclic. Examples which may be mentioned are hexamethylenediamine,piperazine, 1-aminoethylpiperazine, bisaminopropylpiperazine,tetramethylenediamine, octa-methylenediamine, decamethylenediamine,dodecamethylene-diamine, 1,5-diaminohexane,2,2,4-trimethyl-1,6-diamino-hexane, diamine polyols, isophoronediamine(IPD), methylpentamethylenediamine (MPDM), bis(aminocyclohexyl)-methane(BACM) and bis(3-methyl-4-aminocyclohexyl)methane (BMACM).

[0073] In the second and third types, the various constituents of thepolyamide block and their proportion are chosen in order to obtain amelting point of less than 150° C. and advantageously between 90° C. and135° C.

[0074] Copolyamides with a low melting point are disclosed in U.S. Pat.No. 4 483 975, DE 3 730 504 and U.S. Pat. No. 5 459 230, and the sameproportions of the constituents are adopted for the polyamide blocks.

[0075] The polyether blocks may represent 5% to 85% by weight of thecopolymer containing polyamide and polyether blocks. The polyetherblocks may contain units other than ethylene oxide units, such as, forexample, propylene oxide or polytetrahydrofuran (which leads topolytetramethylene glycol sequences). It is also possible to usesimultaneously PEG blocks, i.e. those consisting of ethylene oxideunits, PPG blocks, i.e. those consisting of propylene oxide units, andPTMG blocks, i.e. those consisting of tetramethylene glycol units, alsoknown as polytetrahydrofuran. PPG or PTMG blocks are advantageouslyused. The amount of polyether blocks in these copolymers containingpolyamide and polyether blocks is advantageously from 10% to 50% byweight of the copolymer and preferably from 35% to 50%.

[0076] The copolymers containing polyamide blocks and polyether blocksmay be prepared by any means for attaching the polyamide blocks and thepolyether blocks. In practice, two processes are essentially used, onebeing a 2-step process, the other a one-step process.

[0077] The 2-step process consists firstly in preparing polyamide blockscontaining carboxylic end groups by condensation of the polyamideprecursors in the presence of a chain-limiting dicarboxylic acid andthen, in a second step, in adding the polyether and a catalyst.

[0078] Once the polyamide containing carboxylic acid end groups has beenprepared, the polyether and a catalyst are then added. The polyether maybe added in one or more portions, as may the catalyst.

[0079] The catalyst is defined as being any product which facilitatesthe bonding of the polyamide blocks and the polyether blocks byesterification. The catalyst is advantageously a derivative of a metal(M) chosen from the group formed by titanium, zirconium and hafnium.

[0080] This process and these catalysts are disclosed in patents U.S.Pat. No. 4,332,920, U.S. Pat. No. 4,230,838, U.S. Pat. No. 4,331,786,U.S. Pat. No. 4,252,920, JP 07145368A, JP 06287547A and EP 613919.

[0081] As regards the one-step process, all the reagents used in thetwo-step process, i.e. the polyamide precursors, the chain-limitingdicarboxylic acid, the polyether and the catalyst, are blended. Theseare the same reagents and the same catalyst as in the two-step processdisclosed above. If the polyamide precursors are only lactams, it isadvantageous to add a small amount of water.

[0082] The copolymer essentially has the same polyether blocks and thesame polyamide blocks, but also a small portion of different reagentswhich have reacted randomly and which are distributed randomly along thepolymer chain.

[0083] Advantageously, (C) will be chosen such that it makes it possible“as a bonus” to use a smaller amount of (B) to obtain a transparentcomposition.

[0084] As regards the supple polyamide (C) consisting of copolyamide,this results either from the condensation of at least one α,ω-aminocarboxylic acid (or a lactam), at least one diamine and at leastone dicarboxylic acid, or from the condensation of at least two α,ω-aminocarboxylic acids (or their possible corresponding lactams or of alactam and of the other in α, ω-aminocarboxylic acid form). Theseconstituents have already been defined above.

[0085] As examples of copolyamides, mention may be made of copolymers ofcaprolactam and of lauryllactam (PA 6/12), copolymers of caprolactam, ofadipic acid and of hexamethylenediamine (PA 6/6-6), copolymers ofcaprolactam, of lauryllactam, of adipic acid and of hexamethylenediamine(PA 6/12/6-6), copolymers of caprolactam, of lauryllactam, of11-aminoundecanoic acid, of azelaic acid and of hexamethylenediamine (PA6/6-9/11/12), copolymers of caprolactam, of lauryllactam, of11-aminoundecanoic acid, of adipic acid and of hexamethylenediamine (PA6/6-6/11/12), copolymers of lauryllactam, of azelaic acid and ofhexamethylenediamine (PA 6-9/12). The preferred copolyamides arecopolyamides with a pronounced copolymeric nature, i.e. with essentiallyequivalent proportions of the various comonomers, which leads toproperties that are the furthest removed from the correspondingpolyamide homopolymers. It would not constitute a departure from thecontext of the invention if (C) was a blend of several copolymerscontaining polyamide blocks and polyether blocks or of severalcopolyamides or any combination of these possibilities.

[0086] As regards the compatibilizer (D) of (A) and (B), this is anyproduct which reduces the temperature required to make the blend of (A)and (B) transparent. It is advantageously a polyamide. For example, if(A) is PA 12, then (D) is PA 11. Preferably, it is a catalysed aliphaticpolyamide.

[0087] As regards the catalysed polyamide (D), this is a polyamide asdescribed above for (A), but containing a polycondensation catalyst suchas a mineral or organic acid, for example phosphoric acid. The catalystmay be added to the polyamide (D) after it has been prepared, by anyprocess or, quite simply, and preferably, it may be the rest of thecatalyst used for its preparation. The term “catalyed polyamide” meansthat the chemistry continues beyond the steps for synthesis of the baseresin and thus during the subsequent steps of the preparation of thecompositions of the invention. Polymerization and/or depolymerizationreactions may take place very substantially during the blending of thepolyamides (A) and (B) and (D) to prepare the compositions of thepresent invention. Typically, the Applicant believes (without beingbound by this explanation) that the chains continue to polymerize (chainextension) and to be branched (for example bridging by means ofphosphoric acid). Furthermore, this may be considered as a tendencytowards re-equilibrating the polymerization equilibrium, and thus a kindof homogenization. However, it is recommended to dry the polyamidesthoroughly (and advantageously to control the moisture levels carefully)in order to avoid depolymerizations. The amount of catalyst may bebetween 5 ppm and 15 000 ppm of phosphoric acid relative to the resin(D). For other catalysts, for example boric acid, the contents will bedifferent and may be chosen appropriately according to the usualtechniques for the polycondensation of polyamides.

[0088] Advantageously, the proportion of (B) is between 10% and 40% andpreferably between 20% and 40%. Advantageously, the proportion of(C)+(D) is between 5% and 40% and preferably between 10% and 40%.

[0089] The compositions of the invention are manufactured bymelt-blending the various constituents (twin-screw, BUSS® orsingle-screw extruders) according to the usual techniques ofthermoplastics. The compositions may be granulated for the purpose of asubsequent use (it suffices to remelt them) or they may be injecteddirectly into an extrusion or co-extrusion mould or device tomanufacture tubes, plates, films or profiles. A person skilled in theart may readily adjust the compounding temperature to obtain atransparent material; as a general rule, it suffices to increase thecompounding temperature, for example to about 280 or 290° C.

[0090] The compositions of the invention may comprise stabilizers,antioxidants or UV stabilizers.

EXAMPLES

[0091] The following products were used:

[0092] ASAP: amorphous semi-aromatic polyamide PA-12/BMACM, TA/BMACM, IAsynthesized by melt-polycondensation usingbis(3-methyl-4-aminocyclohexyl)methane (BMACM), lauryl-lactam (L12) andisophthalic and terephthalic acid (IA and TA) in a 1/1/0.3/0.7 molarratio.

[0093] PA 11: polyamide 11 with an {overscore (Mw )} of 45 000 to 55000.

[0094] PA 11 cata: a polyamide 11 with an {overscore (Mw )} of 45 000 to55 000 and containing 3 700 ppm of phosphoric acid catalyst.

[0095] PEBA 12: a copolymer containing PA 12 blocks with an {overscore(Mn )} of 4 000 and PTMG blocks with an {overscore (Mn )} of 1 000 andwith an MFI of 4 to 10 (g/10 min at 235° C. under 1 kg).

[0096] PEBA 6: a copolymer containing PA 6 blocks with an {overscore (Mn)} of 1 350 and PTMG blocks with an {overscore (Mn )} of 650 and with anMFI of 3 to 10 (g/10 min at 235° C. under 1 kg).

[0097] PA 12: a polyamide 12 with an {overscore (Mw )} of 45 000 to 55000.

[0098] The results are reported in Table 1 below. The crystallinity isexpressed by the heat of fusion divided by a constant. The modulus offlexure is measured on a sample conditioned for two weeks at 23° C. and50% RH (relative humidity). In the “examples” column, the numberfollowed by “C” means that it is a comparative example.

[0099] The preceding example can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexample. Also, the preceding specific embodiments are to be construed asmerely illustrative, and not limitative of the remainder of thedisclosure in any way whatsoever.

[0100] The entire disclosure of all applications, patents andpublications, and of corresponding French application 0101110, arehereby incorporated by reference.

[0101] From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions. TABLE 1 (A) Semi- (B) (C) crystalline Amorphous PA Supple(D) Light Compounding Modulus of Examples PA ASAP polyamideCompatibilizer transmission temperature m.p. Cristallinity flexure  1 cPA11 <50% 189 22% 1100  2 c PA11 30% >80% 320 1350  3 PA11 30% 20%PEBA12 >80% 320 1050  4 PA11 25% 15% PEBA12 >80% 320 1100  5 c PA12 <50%178 24% 1200  6 c PA12 30% >80% 350 175 1400  7 c PA12 30% <30% 320  8PA12 30% 10% PA11 >80% 335 1350  9 PA12 30% 10% PA11cata >80% 320 135010 PA12 15% 15% PEBA6 10% PA11cata >80% 320 800 11 c PA12 15% 10%PA11cata <75% 12 PA12 25% 24% PA11cata >80% 320 1200 13 PA12 15% 10%PEBA6 24% PA11cata >80% 320 850

1. Transparent composition comprising, by weight, the total being 100%:5 to 40% of an amorphous polyamide (B) which results essentially fromthe condensation of at least one optionally cycloaliphatic diamine, ofat least one aromatic diacid and optionally of at least one monomerchosen from: α,ω-aminocarboxylic acids, aliphatic diacids, aliphaticdiamines, 0 to 40% of a supple polyamide (C) chosen from copolymerscontaining polyamide blocks and polyether blocks and copolyamides, 0 to20% of a compatibilizer (D) for (A) and (B), (C)+(D) is between 2% and50%, with the condition that (B)+(C)+(D) is not less than 30%, thedifference to 100% being a semi-crystalline polyamide (A). 2.Composition according to claim 1, in which (A) is derived from thecondensation of a lactam containing at least 9 carbon atoms, of an α,ω-aminocarboxylic acid containing at least 9 carbon atoms or of adiamine and a diacid such that the diamine or the diacid contains atleast 9 carbon atoms.
 3. Composition according to claim 1 or 2, in which(A) is PA 11 or PA
 12. 4. Composition according to any one of thepreceding claims, in which (A) is an equilibrated polyamide. 5.Composition according to any one of the preceding claims, in which theamorphous polyamide (B) comprises a cycloaliphatic diamine. 6.Composition according to any one of the preceding claims, in which (C)is a copolymer containing polyamide blocks and polyether blocks. 7.Composition according to claim 6, in which the copolymer containingpolyamide blocks and polyether blocks consists of PA 6 or PA 12 blocksand the polyether blocks are PTMG blocks.
 8. Composition according toany one of claims 1 to 5, in which (C) is a copolyamide.
 9. Compositionaccording to any one of the preceding claims, in which (A) is PA 12 and(D) is PA
 11. 10. Composition according to any one of the precedingclaims, in which the compatibilizer (D) is a catalysed polyamide. 11.Composition according to any one of the preceding claims in which (A) isPA 12 and (D) is catalysed PA
 11. 12. Composition according to any oneof claims 1 to 11, in which the proportion of (B) is between 10% and40%.
 13. Composition according to claim 12, in which the proportion of(B) is between 20% and 40%.
 14. Composition according to any one of thepreceding claims, in which the proportion of (C)+(D) is between 5% and40%.
 15. Composition according to claim 14, in which the proportion of(C)+(D) is between 10% and 40%.
 16. Articles consisting of a compositionaccording to any one of the preceding claims, such as plates, films,sheets, tubes and profiles, to the articles obtained byinjection-moulding and in particular to the films and sheets which arethen bonded onto skis.
 17. Articles according to claim 16, which aredecorated, for example, by sublimation, and coated with a transparentprotective layer consisting of the composition according to any one ofclaims 1 to 15.